No Sound from Ear Speaker

Hi

Wondering if you clever people could assist

I have a iphone 5c that has no sound from the ear speaker, i have replaced the front camera flex as well as the little black speaker, but i still cannot get any sound from the ear speaker.

Is there a chip or some other part on the board that controls this, or some obvious software setting

Thank you all

Thank you all for your repsonse

So ive tried the following

1) Tried 2 new ear speakers

2) Tried 2 new flexes

3) Checked connector

All ok no obvious issues, is there a chip or something on the board that may be causing this issue?. If i try a factory reset will that work?

Regards

Ali